This saying means, "the zipper on your pants is open".There is a amusement park in Pittsburgh called Kennywood Park. If you say this to anyone from the Pittsburgh area rest assured they will check their pants immediately.
by Michael Brams April 10, 2007
from the Pittsburgh area, when the zipper of your jeans is down, an 'open fly'. 'Kennywood' refers to a local amusement park.
by markimusb October 25, 2007